1. Field
The disclosure relates to a rotor for a rotary electric machine, and, more specifically, relates to a rotor for a rotary electric machine, which is provided with a rotor core, a rotor shaft inserted onto the rotor core, and a nut screwed onto the rotor shaft, and is used for a rotary electric machine.
2. Description of Related Art
Conventionally, as this type of rotor for a rotary electric machine, a rotor including an armature core, a shaft, and a nut is proposed (for example, see Japanese Patent Application Publication No. 2002-95197 (JP 2002-95197 A)). In the armature core, a cylindrical center hole is provided, and an inner wall forming the center hole has projections. The shaft is inserted into the center hole of the armature core. In the shaft, thread ridges, onto which the nut is screwed, and recessed grooves are formed. The recessed grooves extend in an axial direction of the shaft and have shapes that allow the projections of the armature core to enter the grooves. In this rotary electric machine, as the projections of the armature core enter the recessed grooves, the rotor is restrained from rotating with respect to the shaft. Further, as the nut is screwed onto the thread ridges in the state where the shaft is inserted into the armature core, and the nut is fastened towards the armature core, it is possible to fix the armature core to the shaft sufficiently.
In the rotor for a rotary electric machine stated above, in which the nut screwed onto the thread ridges of the rotor shaft is used to fix the rotor core to the rotor shaft, the thread ridges of the rotor shaft are required to have strength. On the other hand, grooves are commonly formed in the rotor shaft so that projecting portions on an inner peripheral surface of the rotor core enter the grooves. Further, in order to restrain a nut from loosening, it is considered that grooves are provided in the rotor shaft for crimping the nut and the nut is crimped. When such grooves are formed in the rotor shaft, there are no thread ridges of the rotor shaft in areas where the grooves are formed. Therefore, when the grooves for crimping the nut are formed separately from the grooves that receive the projecting portions on the inner peripheral surface of the rotor core in the rotor shaft, there are many areas where no thread ridges of the shaft are present. This could make it impossible to ensure sufficient strength of the thread ridges.